Third generation partnership project (3GPP) mobile communication systems based on a wideband code division multiple access (WCDMA) radio access technique are widely spread all over the world. High-speed downlink packet access (HSDPA) that can be defined as a first evolutionary stage of WCDMA provides 3GPP with a wireless access technique that is highly competitive in the mid-term future. However, since requirements and expectation of users and service providers are continuously increased and developments of competing radio access techniques are continuously in progress, new technical evolutions in 3GPP are required to secure competitiveness in the future. Reduction of cost per bit, increase of service availability, flexible use of frequency bands, simple structure and open interface, proper power consumption of a user equipment, and the like are defined as requirements.
There are one or more cells within the coverage of a base station. A plurality of user equipments can be placed within a cell. Generally, a user equipment performs a random access procedure to access to a network. The random access procedure is used for a variety of purposes, such as for synchronizing between the user equipment and the network or obtaining uplink radio resources for the user equipment.
Since battery capacity of a user equipment is limited, reducing power consumption of the user equipment is one of major technical issues. The random access procedure may be frequently performed to accomplish the variety of purposes. If power consumption of a user equipment is minimized during the random access procedure, the user equipment can be used for a longer time. A method is sought for performing a random access procedure that reduces power consumption of a user equipment.